As the artisan is aware, circa 1960, a new class of alloys steels were introduced, the steels being designated "maraging". These alloys were characterized by a low carbon, iron-nickel or iron-nickel-cobalt matrix which could be readily aged to deliver a high level of strength.
Initially, two types of maraging steels were proposed, one being an 18%-24% nickel-containing cobalt-free version invented by C. G. Bieber (U.S. Pat. No. 3,093,518), the other a nickel-cobalt-molybdenum material discovered by R. F. Decker et al (U.S. Pat. No. 3,093,519). The former class (cobalt-free) never gained commercial success of any importance and have witnessed little use. Among the reasons for this was the lack of toughness otherwise characteristic of the cobalt-containing variety at desired yield strengths. Since the cobalt-containing type manifested an acceptable level of toughness, these steels generated a substantial market. Schedule I sets forth the three standard nominal commercial compositions of the cobalt maraging steels together with approximate corresponding yield strength levels.
______________________________________ Schedule I Yield Strength psi Co Mo Ni Ti Al C ______________________________________ 200,000 8.5 3.25 18 0.2 0.1 0.03 max 250,000 7.5 5.0 18 0.4 0.1 0.03 max 300,00 9.0 5.0 18.5 0.6 0.1 0.03 max ______________________________________